Fueling Problem? Plugged Exhaust?

[SolidState]

Hey Guys,

I have recently done my plugs, wires, and valve cover seals and plug well gaskets. I broke the EGR tube during the foray, so I capped it off. The car ran noticeably better, but not all that more powerful. After about a week, it developed a misfire and a certain raspiness. I figured that it was due to leaking intake gaskets causing an excessively lean condition.

I had the EGR tube silver welded at a local shop, and ordered some new intake gaskets, EGR gaskets and so on. I took the intake off and installed the intake gaskets and checked my previous work. All the plug wells were bone dry. No leaking valve gaskets. So I put it all back together. EGR works well, starts well so on...new TPS helps shifting....

But it still hasn't any power, and there is STILL a misfire. The thing that bothers me the most is that it feels really buzzy...like a 4 cylinder Honda, not the Yamaha built 3.2...

Unplugging the MAF smoothes things out, and the misfire at idle instantly disappears. Drivability is suffering as anything past 3/4 throttle and the thing falls on its face...With the MAF unplugged, it bogs of course, but it is a lot smoother and feels torquier above 4k rpm.

The 'bump' at 4k rpm isn't nearly as noticeable anymore, although I can still hear the secondaries open up. This is especially true at WOT.

Pulling codes reveals a bad left or rear HEGO. I am also getting a fuel pump circuit code and a gurgling after and warm start up.

Possibilities that I have come up with is a plugged exhaust/bad cats, bad O2s (of course), failing fuel pump and a dirty MAF.

Any ideas?

Thanking in advance

 

[SolidState]

Oh...here are the latest codes:

157
158
176
542

The first two I suppose are from me unplugging my MAF.

The third suggests a bad o2. Funny enough, this time I didn't get a 177. I think that is because of the unplugged MAF obviously causing an excessively rich condition.

542 gets me though. People say it is because of the car stalling, but my car has never stalled.

<small>[ May 05, 2003, 09:13 PM: Message edited by: SolidState ]</small>

 

[89 black SHO mtx]

it sounds like a vacum leak ,to me. but copuld be a stopped up cat. any exhaust shop should be able to do a back pressure test to check and see if they are clogged. if your sure about the intake not leaking try a fuel pressure test. but i'm betting on a vacum leak . good luck

 

[SolidState]

Thanks....I'll double check everything....

 

[projectSHO89]

My 89 recently developed a very raspy exhaust also.

I crawled under it while someone feathered the gas pedal and determined that the rasp is coming from inside the Y-pipe just upstream from the junction.

My assumption is the rear cat has broken up and a piece is stuck there causing the noise at certain RPMs. I'm also getting a CEL with an O2 code for that bank. Guess I'll have to swap Y-pipes soon to fix this.

Steve

 

[sdpatt]

The two MAF codes indicate that you have removed the connector while the engine was running (157) and the MAF has an internal short (158). The second could also be caused by a shorted wire in the harness to the MAF, but since the problem clears when you unplug the MAF, it is most likely internal to the MAF's "black box." You will probably need to replace the electronics on the MAF.

The lean O2 sensor code (176) may have been generated by a lean condition and does not indicate the engine was rich. If you had also received the 177 code, the lean/rich extremes may have been the result of the MAF problems. Fix the MAF first then recheck the O2 sensors.

If you have a misfire without a code to indicate a component in the ignition system is faulting, you need to inspect the spark plugs and wires for evidence of spark leaks, proper gapping, or arc tracking.

Check the cats for loose parts. Any marbles rattling around in there?

<small>[ May 06, 2003, 11:05 AM: Message edited by: sdpatt ]</small>

 

[Markus]

SolidState:
Oh...here are the latest codes:

157
158
176
542

The first two I suppose are from me unplugging my MAF.

The third suggests a bad o2. Funny enough, this time I didn't get a 177. I think that is because of the unplugged MAF obviously causing an excessively rich condition.

542 gets me though. People say it is because of the car stalling, but my car has never stalled.

Ignore the 542 for now. A bad O2 sensor will trigger 542/543.

 

[SolidState]

Thanks guys.

I have always had the 176 and 177 since I purchased the car in august, just haven't gotten around to replacing the O2s.

I cleared the codes and haven't unplugged the MAF since then, and it hasn't thrown the 157 or 158 since.

can bad cats/plugged exhaust cause poor gas milage?